During
heat treatment, many features of machined components suffer
distortion.
If the position or dimensions of a groove
are critical to the
performance of a hardened component.David Richards
can offer a simple solution to this problem
- ‘Hard Grooving’. Based on the Top
Notch system, David Richards
supply grooving tools
in a wide range of
sizes from 0.5 mm width upwards. David Richards
supply tools for
circlip and ‘O’ring grooves with controlled
corners or full radii, either
full form for plunging or undersize
for profiling. Using
such surface speeds typical for turning, grooves are machined at
low feed rates (0.01/0.05 mm/rev). The
low feed rate ensures that the swarf is very weak and brittle, decreasing
the likelihood of it breaking the tool. Where there are no interruptions to the cutting path, coolant should
be used to aid evacuation of the swarf and
ensure that the component remains at a stable temperature for ease
of measuring. If the cutting path is interrupted,
an air blast will serve the same purpose without the risk of thermally
shocking the PCBN tool.If
practical, it is better to finish a groove that has been pre- formed
at the soft stage. This ensures uniform hardness around the groove and maintains the structural integrity
of the component. However, if it is acceptable,
satisfactory results are achieved grooving through a hardened layer into the core material.

Successful
applications include grooving case hardened (58 / 63 HRc) splined
shafts and gear teeth, internal circlip grooving hardened EN31 (58 / 60 HRc) bearing components, and producing
profiles in the face of D2 tools steel tools
using Full radii face grooving tools. All operations that would
be time consuming and difficult to grind.Whilst
the Top Notch system offers an ideal base for most grooving tools,
other systems have been employed with excellent
results. It
naturally follows that, since David Richards can produce tools for
‘Hard Grooving’ full and partial form threading
tools, both external and internal, are available for ‘Hard Threading’.
Where the pitch of the thread is large,
or the diameter of the component is small, it must be remembered
that the feed rate required, at the required
surface speed for ‘Hard Turning’ will be relatively fast. But, producing
a 90 mm diameter internal stub Acme thread
150 mm deep, with a 6 mm pitch in 58 HRc Ni-Hard iron, at 120 m/min
from blank bore, though somewhat exciting,
proved a major cost saver.David
Richards have wide experience in the application of these tools
and will be delighted to discuss specific
examples on request.